I doubt that Nick Drake meant Mary Jane to be taken as marijuana. Maybe it was coincidence that it happened to be slang for marijuana? To me, being high has nothing to do with the song. It's just about the mysteries of people and how you can't know the secret thoughts, dreams, and aspirations of people you know, no matter how much you try or spend time around that person.
I doubt that Nick Drake meant Mary Jane to be taken as marijuana. Maybe it was coincidence that it happened to be slang for marijuana? To me, being high has nothing to do with the song. It's just about the mysteries of people and how you can't know the secret thoughts, dreams, and aspirations of people you know, no matter how much you try or spend time around that person.